Project Summary Our response to the world is not simply the sum of what our sensory organs detect, but also how our brain chooses to represent these detections, and act upon them. However, knowledge of how sensory inputs are interpreted by our brains to yield behavioral outputs is lacking. Unlike simple reflexes, the majority of our behaviors are governed by an internal representation of the external world. This internal state is not static; but shows dynamic activity during both awake and sleep periods. In short, we are always thinking. Even in sensory deprived contexts, nearly all regions of our brain remain active. Therefore, the central challenge with predicting behavioral output from sensory input is that our perception of the world is dynamic and highly variable, rendering many behaviors unpredictable. Understanding the functional underpinnings of how internal dynamics arise in complex brains is limited. However, dynamic internal states also influence perception and behavior in simple animals such as Caenorhabditis elegans. It is currently the only organism where we have a detailed map of every neuron and synapse. We can simultaneously manipulate and monitor the activity of every neuron in the brain. This exquisite ability to manipulate specific neurons in a fully mapped brain makes C. elegans the ideal organism to understand the complexity of resting state dynamics in a reduced system. My long-term goal is to understand how neural circuits generate resting state dynamics on different timescales, and how these states influence perception and behavior. Understanding this process will provide a foundation for understanding the learning process, and the principles that govern how behavioral novelty arises and adapts to the environment.